Telephone-exchange system



H. W. MACDOUGALL- TELEPHONE EXCHANGE SYSTEM.

APPLICATION HLED SEPT. 25. 1911.

1,381,483. Patented M514, 1921.

/n l enfor: Harry W/VaaDouga/A by A M UNITED STA'IE PATENT OFFICE.

HARRY W. MACDOUGALL, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COIJIPANY, INGQRPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent. Patented June 14., 1921,

Application filed September 25, 1917. Serial No. 193,108.

To all 'w 710m it may con cern Be it known that I, HARRY V. MAG- DOUGALL, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to such systems in which ringing current is automatically applied to a wanted line upon the connection of a link circuit therewith.

An object of this invention is the production of a system oi this character in which it is impossible to ring the subscriber in the ear.

In accordance with a feature of the invention, a link circuit of the automatic ringing type is provided with apparatus for preventing the connection of a source of ringing' current to a busy line or to a line, the receiver of which is removed from the switchhook when the link circuit is connected with such a line.

Apparatus is also provided by means of which, when the link circuit is connected with a line of the character mentioned, the talking circuit with such line is automatically and immediately established, whereby the talking circuit between the calling subscriber and a called subscriber, may be established without applying ringing current to the wanted line. By utilizing the present invention, an automatic ringing link circuit may be employed for establishing a th ee co nered connection without causing disagreeable clicks in the receivers of any of the subscribers involved.

For a more complete understanding of this invention, reference may be had to the tollowing description considered in conneci with the accompanying drawing illusng one embodiment thereof. in the draw'ng there is shown a telephone lin It. connects .n any desired manner with a cord circuit C which may be employed to connect the calling line A with another telephone line B terminating at the same central otiice. It will be understood that a number of lines similar to lines A and B termimile at the same central ofiice and that a urality of cordcircuits are providedthereat for interconnecting such lines, but for the sake of convenience, only the two lines and the one cord circuit are shown.

Assuming that the operator has been ad- I vised that the calling subscriber A desires to be connected with the line of subscriber B, the operator may thereupon test the terminal of line B in order to determine whether this/line is idle or busy.

Assuming that line B is busy, due to the connection of another cord circuit similar to C with one of its multiple jacks, the cut oil relay 5 of line B will be operated to disconnect line relay 6 from the line. Under these conditions the operator may insert plug 7 of cord circuit C into ack 8 without making the usual busy test; If the plug 7 of the cord circuit C be inserted into the jack 8 while another cord circuit is connected with another ack of the same line, current will flow tromrbattery in the other cord circuit over the ring talking strand thereof and the ring contacts of the engaged plug and jack, the ring contacts of jack 8 and the plug 7, lower normal contact of relay 9, and the winding of relay 10 to ground. Relay l0 thereupon operates, establishing a locking circuit for itself from battery through contact 42 of relay 25 and left-hand contact and winding of relay 10 to ground, and causing the energization of relay 9 over a circuit from battery through the right-hand contact of relay 10, winding of relay 9, sleeve contacts of the plug 7 and jack 8, and the winding of cut-oil? relay to ground. Relay 9, upon being energized, establishes a looking circuit for itself through its alternate contact 11. The locking circuit of relay 10 is provided to insure that relay 9 is locked up before the right-hand contact of relay 10 in the energizing circuit of relay 9 can be opened. Relay 9 also establishes a circuit for the slow operating relay 12 and the supervisory relay lamp 31. which lights, and closes a contact in circuit with fast operating relay 13.

Assuming that the subscriber of line B has the receiver removed from the switchhook when relay 9 is energized, supervisory relay l4 and fast operating relay 13 will be immediately energized over a circuit from battery through repeating coil winding 15, windings of supervisory relay 14.- and fast operating relay 18, lower normal contact of ringing relay 16, alternate contact 17 of relay 9, ring contacts of the plug 7 and the jack 8, over one side of line B, through substation apparatus and switchhook contact, back over the other side of line B, tip contacts of the jack 8 and the plug 7, alternate contact 18 of relay 9, upper normal contact of ringing relay 16, and repeating coil winding to ground. Fast operating relay 13 is immediately energized opening its normal and closing its alternate contact. Since the energizing circuits of the fast operating relay 13 and the slow operating relay 12 are closed at the same time, relay 13 will attract its armatures before the slow operating relay 12 attracts its armature, therefore the energizing circuit of the ringing relay 16 will be opened at the normal contact of relay 13 before it can be closed at the alternate contact of relay 1 Relay 16 is therefore prevented from being energized and ringing current from a source 20 cannot be connected with the telephone line B.

Upon the closure of the alternate contact of relay 12 when this relay is fully energized, relay is operated over a circuit from bat.- tery through the winding of relay 25, alternate contact of fast operating relay 13, and the contact of slow operating relay 12 to ground. Relay 25 in operating establishes a locking circuit for itself which may be traced from battery through the winding of relay 25, contact 26 thereof, and the contact of relay 12 to ground. Relay 25 in operating also closes its contact 27, thereby establishing a short-circuit for fast operating relay 13, thereby removing this relay 13 from the talking circuit and causing the release thereof. Contact 412 in the locking circuit of relay 10 is opened when relay 25 operates, whereupon relay 10 releases.

The consequent closing of the normal contact of relay 13 does not complete the energizing circuit of the ringing relay 16, for it is open at contact 28 of relay 25, which is now locked up. The energization of supervisory relay 14 connects a shunt including resistance 30 about calling supervisory lamp 31, thereby preventing the continued lighting of this lamp.

At the conclusion of the conversation, the restoration of the receiver at station B to the switchhook causes the release of relay 14, whereupon the supervisory lamp 31 is lighted to furnish a disconnect signal. The operator may then withdraw the plug 7 from the jack 8, whereupon all apparatus is restored to normal position.

If when the plug 7 is inserted in the jack 8 no other cord circuit is connected with the jack of line B, but the receiver at the station is removed from the switchhook, relay 10 will then be energized from battery through the right-hand winding of line relay 6, righthand contact of cut-off relay 5, ring contacts in the jack 8 and plug 7, lower normal contact of relay 9, and the winding ofrelay 10 to ground. Relay 9 is then energized over the same circuit hereinbefore traced in connection with the description of the operation involved when the plug 7 is connected with the jack of a line to which another cord circuit is already connected. The apparatus functions in precisely the same manner as hereinbefore described to prevent the connection of ringing current to line B and to complete the talking circuit.

If no other cord circuit is connected with line B and the receiver is not removed from its switchhool: when the plug 7 is inserted in the jack 8, the circuit of fast operating relay 13 is not then closed upon the energization of relay 9, so that upon the operation of slow operating relay 12, ringing relay 16 is energized over the circuit from battery through the winding of ringing relay 16, normal contact of relay 13, contact 38 of relay 25 (or contact of tripping relay 35 and contact 28 of relay 25), and the contact of relay 12 to ground. Relay 16 upon being energized, connects ringing current to line 13 over a circuit which may be traced from the source of ringing current 20 through the winning of tripping relay 35, lower alternate contact of ringin relay 16, contact 1.? of relay 9, ring contacts of the plug 7 and the jack 8, call bell 36 and condenser 37, tip contacts of the jack 8 and the plug 7, contact 18 of relay 9, and the upper alternate contact of ringing relay 16 to ground. T pon the encrgization of ringing relay 16, relay 25 is operated over a circuit from battery through the winding of relay 25, middle alternate contact of relay 16, contact 28 of relay 25 (or contact of tripping relay 35 and contact 38 of relay 25), and the contact of relay 12 to ground. Relay 25 in operating establishes a locking circuit for itself which may be traced to battery through the inding of relay 25, contact 26 thereof, and the contact of relay 12 to ground. Relay 25 in operating also establishes a locking circuit of relay 16, which may be traced from battery to relay 16, normal contact of relay 13, contact of tripping relay 35, middle alternate contact of relay 16', contact 26 of relay 25, and the contact of relay12 to ground. The closure of contact 2? of relay 25 establishes a short circuit for relay 13, removing this relay from the talking circuit.

Upon the response of the called subscriber V to the operation of the call bell 36, the receiver is removed from the switchhook, whereupon tripping relay 35 is operated to open its contact, thereby opening the looking circuit of ringing relay 16. Ringing relay 16 thereupon releases its armatures,

disconnecting ringing current from the called line and closing its upper and lower alternate contacts to short-circuit condensers 40 and 41, thereby eliminating these condensers from the talking circuit. Upon the release of ringing relay 16, the calling supervisory relay 14 is operated to efface the calling supervisory lamp 31.

Upon the conclusion of the conversation, the restoration of the receiver to the switchhook-by subscriber B, causes the release of supervisory relay 14, whereupon the lamp is lighted to furnish a disconnect signal. The operator may then withdraw the plug 7 from the jack 8, thereby restoring all apparatus to normal condition.

What is claimed is:

1. In a telephone exchange system, in combination, a telephone line, a link circuit, a relay in the link circuit energized upon connection of the link circuit with the telephone line, a slow operating relay in the link circuit, an energizing circuit therefor completed upon the energization of the first relay, a source of ringing current, a ringing relay when operated connecting the source of ringing current to the telephone line and having an operating circuit controlled by the slow operating relay, and a fast operating relay operating upon the energization of the first relay when the telephone line is closed to disable the operating circuit of the ringing relay.

2. In a telephone exchange system, in combination, a telephone line, a link circuit, a relay in the link circuit energized upon connection of the link circuit with the tele phone line, a slow operating relay in the link circuit, an energizing circuit therefor completed upon the energization of the first relay, a source of ringing current, a ringing relay when operated connecting the source of ringing current to the telephone line and having an operating circuit controlled by the. slow operating relay, a fast operating relay energized upon the energization of the first relay when the telephone line is closed to disable the operating circuit of the ringing relay, a local relay'energized upon the energization of the fast operating relay to cause the de'e'nergization of the fast operating relay and to open a contact in the operating circuit of the ringing relay, a locking circuit for the local relay, established upon the energization thereof for rendering this local relay independent of the fast operating relay.

In a telephone exchange system, in combination, a telephone line, a link circuit, a relay in the link circuit energized upon connection of the-link circuit with the telephone line, a slow operating relay, an energizing circuit therefor completed upon the energization of the first relay, a source of ringing current, a ringing relay when operated connecting the source of ringing our? rent to the calling line and having an operating circuit controlled by the slow operating relay, and a fast operating relay having a normally closed contact in the operating circuit of the ringing relay and operating upon the energization of the first relay when the telephone line is closed to open the contact of the operating circuit in the ringing relay.

In a telephone exchange system, in combination, a telephone line, a link circuit having a talking conductor, a relay in the link circuit energized upon connection of the link circuit with the telephone line, a slow operating relay, an energizing circuit therefor completed upon the energization of the first relay, a source of ringing current a ringing relay when operated connecting the source of ringing current to the telephone line and having an operating circuit controlled by the slow operating relay, a fast opera-ting relay operating over a circuit including the talking conductor upon the energization of the first relay when the telephone line is closed to disable the operating circuit of the ringing relay.

5. In a telephone exchange system, in combination, a telephone line, a link circuit having a talking conductor, a relay in the link circuit energized upon connection of the link circuit with the telephone line, a slow operating relay, an energizing circuit therefor completed upon the energization of the first relay, a source of ringing current, a ringing relay when operated connecting the source of ringing current to the telephone line and having an operating circuit controlled by the slow operating relay, a fast operating relay connected in the talking conductor and operating upon the energization of the first relay when the telephone line closed to disable the operating circuit of the ringing relay, electromagnetic means responsive to the operation of the fast relay, and circuit connections established upon the response of the electromagnetic means for eliminating the fast operating relay from the talking conductor.

(3. In a telephone exchange system, in combination, a relay in the link "ircuit energized upon connection of the link circuit with the telephone line. a slow operating relay, an energizing circuit therefor completed upon the energization of the first relay. a source of ringing current, a ringing relay when operated connecting the source of ringing current to the telephone line and having an operating circuit controlled by the slow operating relay, a. fast operating relay connected in the talking conductor and operating upon the energization of the first relay when the telephone line is closed to disable the operating circuit of the ringing relay, a local relay energized upon the operation of the fast operating relay, and a short circuit for the fast operating relay established upon the energization of the local relay whereby the fast operating relay is removed from the talking circuit.

7. In a telephone exchange system, n combination, a telephone line, a link circuit haying a talking conductor, a relay in the link circuit energized upon connection thereof with a telephone line, a source of ringing current, a ringing relay when energized for connecting the source of ringing current to the telephone line, a relay in the talking circuit, an energizing circuit therefor controlled by the ringing relay completed upon the energization of the first relay when the ringing relay is deenergized and when the telephone line is closed where by the talking circuit relay is energized to disable the energizing circuit of the ringing rela and a local circuit relay energized and locked up upon the operation of the talking circuit relay for removing said relay from the talking circuit.

8. In a telephone exchange system, in combination, a telephone line, a link circuit having a talking conductor, a relay in the link circuit energized upon connections thereof with a telephone line, a source of ringing current, a ringing relay when energized connecting the source of ringing current to the telephone line, a talking circuit relay, an energizing circuit therefor including a normally closed contact of the ringing relay completed upon the energization of the first relay when the telephone line is closed whereby the talking circuit relay is energized for disabling the initial energizing circuit of the ringing relay.

9. In a telephone exchange system, in combination, a telephone line, a link circuit having a talking conductor, a relay in the link circuit energized upon the connection thereof with a telephone line, a source of ringing current, a rin ing relay when energized con necting the source of ringing current to the telephone line, a relay in the talking conductor, an energizing circuit therefor including a normally closed contact of the ringing relay and a contact of said first relay completed upon the operation of the first men tioned relay when the telephone line is closed whereby the talking circuit relay is energized to disable the energizing circuit of the ringing relay, a local circuit relay energized upon the operation of the talking circuit relay, a locking circuit therefor completed upon the energization thereof and circuit connections rendered effective upon the energization of the local relay to eliminate the relay from the talking conductor.

10. In a telephone exchange system, in combination, a telephone line terminating in a plurality of terminals, a link circuit connected with one of the terminals, a

second linkcircuit comprising talking conductors, a relay in the second link energized over a circuit including a portion of the first link upon connecting the second link with the engaged telephoneline, a second relay energized and locked up upon the energization of the first relay, a source of ringing current, a ringing relay when energized connecting the source of ringing current to the telephone line, an energizing circuit therefor controlled by the second relay, a relay in the talking circuit having a normally closed contact in the energizing circuit of the ringing relay and operating upon the energization of the second relay when the second link circuit is connected with the engaged line to open the normally closed contact. 7

11. In a telephone exchange system, in combination, a telephone line terminating ina plurality of terminals, a link circuit connected with one of the terminals, a second link circuit comprising talking conductors, a relay in the second link energized over a circuit including a portion of the first link upon connection of the second link with the engaged telephone line, a second relay energized and locked up upon the energization of the first relay, a source of ringing current, a ringing relay when energized connecting the source ofringing current to the telephone line, an energizing circuit therefor, controlled by the second relay, a relay in the talking circuit having a normally closed contact in the energizing circuit of the ringing relay and operating upon the energization of the second relay when the second cord circuit is connected with the engaged line to open the normally closed contact, and a local relay energized and locked up upon the operation ofthe talking circuit relay for removing said relay from the talking circuit.

12. In a telephone exchange system, in combination, a telephone line, a link circuit, a talking conductortherefor having a normally open contact, a relay operating upon connection of the link circuit with the telephone line, a source of ringing current, a

ringing relay when energized connecting the source of ringing current with the telephone line, an energizing circuit for the ringing relay controlled by the first relay, a relay bridging the normally open contact of the talking conductor and energized upon the operation of the first relay when the telephone line is closed to disable the energizing circuit of the ringing relay, and electromagnetic means responsive to the energization of the bridging relay to close the contact in the talking conductor.

In witness whereof, I hereunto subscribe my name this 21st day of September, A. D., 1917.

HARRY W. MAODOUGALL. 

